Meats, poultry, and other food items have typically been smoked in smokehouse-type systems. Smokehouse systems commonly involve batch-type operations wherein food items are placed in cages, or on racks, which are then placed in a smoking chamber. In the smoking chamber, smoke circulates down the sides and then up through the center of the chamber. The smoking process typically involves (1) a heat-up cycle wherein moisture is removed from the surfaces of the food items in order to prepare the items for smoking, followed by (2) a smoking cycle.
Smokehouse operations have many shortcomings. For example, batch-type smoking operations for poultry items commonly require five to seven hours or more. In addition to being inefficient, these slow smoking processes can sometimes impart an extremely dark color and/or an overpowering smoke flavor to the food items. Smokehouses commonly also do not provide desirably uniform temperature and smoke profiles. The existence of hot spots and low smoke points within the smoking chamber can cause substantial variations in the nature and quality of the products produced.
Some smokehouse operations have been modified to include means for pushing the smoking racks/cages through the smoking chamber or through a series of chambers wherein different phases of the smoking process are conducted. U.S. Pat. No. 4,976,009 discloses a smokehouse assembly including a sequence of processing chambers and a trolley assembly for carrying meat racks through the chambers. Each chamber includes an internal diffuser panel which is intended to provide improved air distribution within the chamber. A heat exchanger assembly is mounted in each chamber above a fan. The fan moves air downwardly from the heat exchanger, through the diffuser panel, and then over the meat items hanging on the rack.
Unfortunately, the use of a trolley-type system to push product racks or cages through sequential smoking chambers or zones does not resolve the problems mentioned above. Such smoking processes are still slow, still require a relatively high level of product handling, and are therefore costly and inefficient. Additionally, due to the length and nature of the smoking process, the products produced therefrom tend to be very dark in color and can have an overpowering smoke flavor. Further, non-uniform temperature and smoke profiles within the chambers can result in substantial variations in the nature and quality of the products produced.
Continuous fired ovens and continuous indirectly heated ovens are known in the art. To our knowledge, no one has heretofore used such continuous ovens for simultaneously cooking and smoking food items.
An indirect heated, continuous impingement oven 2 of a type known in the art is depicted in FIG. 1. The oven comprises: a housing 4 including a base portion 6 and a liftable hood 8; a belt-type conveyor 10 for continuously conveying food items through the oven; a circulation system 12 for circulating a cooking medium (preferably air) through the oven; at least one burner 14 or other heating device for indirectly heating the cooking medium; and impingement headers 15 positioned above and below conveyor 10. Impingement headers 15 include a plurality of impingement nozzles, impingement orifices, and/or other such impingement structures 16. As will be understood by those skilled in the art, impingement devices 16 are operable for applying the cooking medium to the food items in an impinging manner.
Circulation system 12 will typically include at least one fan or other type of blower 17 which draws (recirculates) the cooking medium 13 from oven chamber 18 into blower inlet 19 and then delivers the cooking medium through impingement structures 16. Circulation system 12 will also typically include a heating element and/or heating chamber wherein burner 14 indirectly heats the cooking medium to a desired cooking temperature. Because the cooking medium is indirectly heated by burner 14, the combustion product produced by burner 14 (i.e., flames and combustion gases) does not contact either the cooking medium or the food products.
If allowed to contact food items such as poultry, combustion gases can act as curing agents and impart a raw, pink color to the meat. The end user of the product could therefore mistakenly believe that the product is not thoroughly cooked. For this and other reasons, indirect- fired ovens are generally preferred over direct-fired ovens for at least certain types of cooking operations.
Impingement structures 16 are positioned above, below, and across the width of conveyor 10 to thereby completely envelope the food items in a high velocity cooking atmosphere. Thus, each food item is properly cooked, regardless of its position on conveyor 10. Such uniformity minimizes overcooking and provides optimal yields. Conveyor 10 preferably utilizes a low density (highly porous) belt to ensure good air contact on the bottoms of the food items.
Continuous impingement oven 2 will also typically include: a steam system for humidifying the cooking atmosphere; systems for selecting and controlling temperatures, humidities and air velocities; means for adjusting nozzle height and conveyor height; a hoist for lifting oven hood 8; and a sealing system (e.g., a water seal) for sealing the sides of oven 2 when hood 8 is lowered onto base 6.
It is also typical that oven 2 be divided into a plurality of cooking zones and/or that a plurality of ovens 2 be operably linked together. When linked together in series, the ovens 2 will commonly employ a single conveyor 10 which extends through all of the ovens. A different set of cooking parameters can be employed in each individual zone and/or oven. In multizone systems, it is typical that a relatively high heat input be used in the first zone in order to bring the product up to cooking temperature. Less heat is needed in subsequent zones since the product need only be maintained at cooking temperature.
An indirect heated continuous spiral oven 22 of a type known in the art is depicted in FIG. 2. Spiral oven 22 comprises: an oven housing 24 having a cooking chamber 25; a spiral, belt-type conveyor system 26 for conveying food items through oven chamber 25; a circulation system 28 for circulating a cooking medium (preferably air) through chamber 25; and at least one burner or other heating device 30. Circulation system 28 includes at least one fan or other type of blower 31 and has a blower inlet 32. As with the heating device 14 used in impingement oven 2, heating device 30 is preferably operable for indirectly heating the cooking medium so that none of the heating medium/combustion product produced by device 30 contacts either the cooking medium or the food items.
Circulation system 28 and heating device 30 operate in substantially the same manner as the circulation system 12 and heating device 14 of impingement oven 2 except that the spiral oven circulation system 28 typically does not include an impingement system. Rather, circulation system 28 delivers the heated cooking medium into cooking chamber 25 such that the cooking medium passively contacts and heats the food items conveyed on spiral conveyor 26. Spiral conveyor 26 will typically employ a dense belt (i.e., a belt which is either nonporous or has a low porosity) such that, when circulating system 28 delivers the hot cooking medium to the top of spiral conveyor 26, the cooking medium generally flows in a passive manner down the spiral belt (i.e., generally parallel to the belt) to the bottom of the oven.
Because spiral oven 22 employs a passive contacting system rather than an impingement system, the required cooking time in spiral oven 22 will typically be greater than the cooking time required in impingement oven 2. For poultry products, the cooking time in a continuous spiral oven 22 will typically be in the range of from about 40 minutes to about 1 hour as compared to a cooking time in a continuous impingement oven 2 in the range of from about 10 to about 25 minutes.